projects/linux·blob v2.6.29-rc3 · refs

199 lines · 4.5 KiB

1/* Copyright 2008, 2005 Rusty Russell [email protected] IBM Corporation.
2 * GPL v2 and any later version.
3 */
4#include <linux/cpu.h>
5#include <linux/err.h>
6#include <linux/kthread.h>
7#include <linux/module.h>
8#include <linux/sched.h>
9#include <linux/stop_machine.h>
10#include <linux/syscalls.h>
11#include <linux/interrupt.h>
12
13#include <asm/atomic.h>
14#include <asm/uaccess.h>
15
16/* This controls the threads on each CPU. */
17enum stopmachine_state {
18 /* Dummy starting state for thread. */
19 STOPMACHINE_NONE,
20 /* Awaiting everyone to be scheduled. */
21 STOPMACHINE_PREPARE,
22 /* Disable interrupts. */
23 STOPMACHINE_DISABLE_IRQ,
24 /* Run the function */
25 STOPMACHINE_RUN,
26 /* Exit */
27 STOPMACHINE_EXIT,
28};
29static enum stopmachine_state state;
30
31struct stop_machine_data {
32 int (*fn)(void *);
33 void *data;
34 int fnret;
35};
36
37/* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */
38static unsigned int num_threads;
39static atomic_t thread_ack;
40static DEFINE_MUTEX(lock);
41/* setup_lock protects refcount, stop_machine_wq and stop_machine_work. */
42static DEFINE_MUTEX(setup_lock);
43/* Users of stop_machine. */
44static int refcount;
45static struct workqueue_struct *stop_machine_wq;
46static struct stop_machine_data active, idle;
47static const cpumask_t *active_cpus;
48static void *stop_machine_work;
49
50static void set_state(enum stopmachine_state newstate)
51{
52 /* Reset ack counter. */
53 atomic_set(&thread_ack, num_threads);
54 smp_wmb();
55 state = newstate;
56}
57
58/* Last one to ack a state moves to the next state. */
59static void ack_state(void)
60{
61 if (atomic_dec_and_test(&thread_ack))
62 set_state(state + 1);
63}
64
65/* This is the actual function which stops the CPU. It runs
66 * in the context of a dedicated stopmachine workqueue. */
67static void stop_cpu(struct work_struct *unused)
68{
69 enum stopmachine_state curstate = STOPMACHINE_NONE;
70 struct stop_machine_data *smdata = &idle;
71 int cpu = smp_processor_id();
72 int err;
73
74 if (!active_cpus) {
75 if (cpu == cpumask_first(cpu_online_mask))
76 smdata = &active;
77 } else {
78 if (cpumask_test_cpu(cpu, active_cpus))
79 smdata = &active;
80 }
81 /* Simple state machine */
82 do {
83 /* Chill out and ensure we re-read stopmachine_state. */
84 cpu_relax();
85 if (state != curstate) {
86 curstate = state;
87 switch (curstate) {
88 case STOPMACHINE_DISABLE_IRQ:
89 local_irq_disable();
90 hard_irq_disable();
91 break;
92 case STOPMACHINE_RUN:
93 /* On multiple CPUs only a single error code
94 * is needed to tell that something failed. */
95 err = smdata->fn(smdata->data);
96 if (err)
97 smdata->fnret = err;
98 break;
99 default:
100 break;
101 }
102 ack_state();
103 }
104 } while (curstate != STOPMACHINE_EXIT);
105
106 local_irq_enable();
107}
108
109/* Callback for CPUs which aren't supposed to do anything. */
110static int chill(void *unused)
111{
112 return 0;
113}
114
115int stop_machine_create(void)
116{
117 mutex_lock(&setup_lock);
118 if (refcount)
119 goto done;
120 stop_machine_wq = create_rt_workqueue("kstop");
121 if (!stop_machine_wq)
122 goto err_out;
123 stop_machine_work = alloc_percpu(struct work_struct);
124 if (!stop_machine_work)
125 goto err_out;
126done:
127 refcount++;
128 mutex_unlock(&setup_lock);
129 return 0;
130
131err_out:
132 if (stop_machine_wq)
133 destroy_workqueue(stop_machine_wq);
134 mutex_unlock(&setup_lock);
135 return -ENOMEM;
136}
137EXPORT_SYMBOL_GPL(stop_machine_create);
138
139void stop_machine_destroy(void)
140{
141 mutex_lock(&setup_lock);
142 refcount--;
143 if (refcount)
144 goto done;
145 destroy_workqueue(stop_machine_wq);
146 free_percpu(stop_machine_work);
147done:
148 mutex_unlock(&setup_lock);
149}
150EXPORT_SYMBOL_GPL(stop_machine_destroy);
151
152int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
153{
154 struct work_struct *sm_work;
155 int i, ret;
156
157 /* Set up initial state. */
158 mutex_lock(&lock);
159 num_threads = num_online_cpus();
160 active_cpus = cpus;
161 active.fn = fn;
162 active.data = data;
163 active.fnret = 0;
164 idle.fn = chill;
165 idle.data = NULL;
166
167 set_state(STOPMACHINE_PREPARE);
168
169 /* Schedule the stop_cpu work on all cpus: hold this CPU so one
170 * doesn't hit this CPU until we're ready. */
171 get_cpu();
172 for_each_online_cpu(i) {
173 sm_work = percpu_ptr(stop_machine_work, i);
174 INIT_WORK(sm_work, stop_cpu);
175 queue_work_on(i, stop_machine_wq, sm_work);
176 }
177 /* This will release the thread on our CPU. */
178 put_cpu();
179 flush_workqueue(stop_machine_wq);
180 ret = active.fnret;
181 mutex_unlock(&lock);
182 return ret;
183}
184
185int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
186{
187 int ret;
188
189 ret = stop_machine_create();
190 if (ret)
191 return ret;
192 /* No CPUs can come up or down during this. */
193 get_online_cpus();
194 ret = __stop_machine(fn, data, cpus);
195 put_online_cpus();
196 stop_machine_destroy();
197 return ret;
198}
199EXPORT_SYMBOL_GPL(stop_machine);